Compositions for inhibiting the development of tolerance to and/or dependence on an additive substance

Abstract: Nontoxic substances that block the N-methyl-D-aspartate (NMDA) receptor, e.g., a morphinan such as dextromethorphan or dextrorphan, or that block a major intracellular consequence of NMDA receptor activation, e.g., a ganglioside such as GM₁ or GT 1b , a phenothiazine such as trifluoperazine or a naphthalenesulfonamide such as N-(6-aminohexyl)-5-chloro-1-naphthalenesulfonamide, inhibit the development of tolerance to and/or dependence on addictive drugs, e.g., narcotic analgesics such as morphine, codeine, etc.

Description: BACKGROUND OF THE INVENTION This invention relates to a composition containing an addictive substance and a component which inhibits the development of tolerance to and/or dependence on the addictive substance. More particularly, the invention relates to a composition containing an addictive substance such as morphine or codeine and at least one nontoxic substance that blocks the N-methyl-D-aspartate (NMDA) receptor, e.g., a morphinan such as dextromethorphan or dextrorphan. Morphine is a rapid and effective drug for the treatment of severe pain but its long term administration has been limited due to its negative side effects, principally tolerance and dependence, which develop rapidly after administration. In an effort to make morphine of greater use in the treatment of pain, it has been combined with a variety of substances intended to inhibit one or more of its undesirable side effects. U.S. Patent No. 2,770,569 describes the combination of morphine with the compound levo-d-hydroxy-N-allyl-morphinan which is said to suppress or eliminate such undesirable side reactions of morphine as depression, nausea and vomiting. U.S. Patent No. 4,126,684 discloses reducing either the addiction liability of an addictive substance such as a narcotic analgesic or a barbiturate or the withdrawal symptoms caused by deprivation of such a substance in an addicted subject by administering the addictive substance, e.g., morphine, with a 4-amino-3-p-halophenylbutyric acid. U.S. Patent No. 4,415,871 describes the prevention of treatment tolerance and physical dependence in chronic morphine treatment by combining the morphine with any of the specific dipeptides indicated therein. U.S. Patent No. 5,041,446 discloses inhibiting the development of tolerance to morphine by combining the morphine with dapiprazole. U.S. Patent No. 5,057,519 achieves a reduction in morphine tolerance by combining the morphine with a benzamide antagonist for a subtype of the serotonin receptor, 5-HT 3 . Trujillo et al., "Inhibition of morphine tolerance and dependence by the NMDA receptor antagonist MK-801", Science, 251 (4989), pp. 85-87, January 4, 1991; Tanganelli et al., "Glutamate antagonists prevent morphine withdrawal in mice and guinea pigs", Neuroscience Letters, 122(2), pp. 270-272, January 28, 1991; Marek et al., "Excitatory amino acid antagonists (kynurenic acid and MK-801) attenuate the development of morphine tolerance in the rat", Brain Research, 547(1), pp. 77-81, April 26, 1991; and, Marek et al., "Delayed application of MK-801 attenuates development of morphine tolerance in rats, Brain Research, 558(1), pp. 163-165, August 30, 1991 discuss the role of MK-801 (the compound 5-methyl-10,11-dihydro-SH-dibenzo[a,d]cyclohepten-5,10-imine), an NMDA receptor antagonist or blocker, in reducing morphine dependence in laboratory animals. However, MK-801 has been found to be toxic and is therefore unsuitable for pharmaceutical use. SUMMARY OF THE INVENTION In accordance with the present invention, a pharmaceutical composition is provided which comprises an addictive substance and at least one nontoxic substance that blocks the N-methyl-D-aspartate receptor and/or at least one substance that inhibits the development of tolerance to and/or dependence on the addictive substance and selected from the group consisting of morphinans, their mixtures and their pharmaceutically acceptable salts. The term "nontoxic" as used herein shall be understood in a relative sense and is intended to designate any substance that has been approved by the United States Food and Drug Administration ("FDA") for administration to humans or, in keeping with established criteria, is susceptible to approval by the FDA for administration to humans. BRIEF DESCRIPTION OF THE DRAWINGS: Figs. 1-2 are graphical representations of experimental data demonstrating the effectiveness of specific nontoxic substances that block the N-methyl-D-aspartate receptor or a major consequence of N-methyl-D-aspartate receptor activation for inhibiting morphine tolerance and dependence in rats. DESCRIPTION OF THE PREFERRED EMBODIMENTS A particularly important category of addictive substances with which the present invention is concerned are the narcotic analgesics, e.g., opiates, opiate derivatives, opioids and their pharmaceutically acceptable salts. Specific examples of narcotic analgesics include alfentanyl, alphaprodine, anileridine, bezitramide, codeine, dihydrocodeine, diphenoxylate, ethylmorphine, fentanyl, heroin, hydrocodone, hydromorphone, isomethadone, levomethorphan, levorphanol, metazocine, methadone, metopon, morphine, opium extracts, opium fluid extracts, powdered opium, granulated opium, raw opium, tincture of opium, oxycodone, oxymorphone, pethidine, phenazocine, piminodine, racemethorphan, racemorphan, thebaine and pharmaceutically acceptable salts thereof. For a detailed discussion of these and other narcotic analgesics, reference may be made to Jaffe et al., "Opioid Analgesics and Antagonists" in "Goodman and Gillman's Pharmacological Basis of Therapeutics", Goodman et al., eds. 7th ed., 1985, MacMillan and Company, New York pp. 491-531. Other addictive substances that can be utilized herein include acetorphine, acetyldihydrocodeine, acetylmethadol, allylprodine, alphracetylmethadol, alphameprodine, alphamethadol, benzethidine, benzylmorphine, betacetylmethadol, betameprodine, betamethadol, betaprodine, clonitazene, cocaine, codeine methylbromide, codeine-N-oxide, cyprenorphine, desomorphine, dextromoramide, diampromide, diethylthiambutene, dihydromorphine, dimenoxadol, dimepheptanol, dimethylthiamubutene, dioxaphetyl butyrate, dipipanone, drotebanol, ethanol, ethylmethylthiambutene, etonitazene, etorphine, etoxeridine, furethidine, hydromorphinol, hydroxypethidine, ketobemidone, levomoramide, levophenacylmorphan, methyldesorphine, methyldihydromorphine, morpheridine, morphine methylpromide, morphine methylsulfonate, morphine-N-oxide, myrophin, nicocodeine, nicomorphine, nicotine, noracymethadol, norlevorphanol, normethadone, normorphine, norpipanone, phenadoxone, phenampromide, phenomorphan, phenoperidine, piritramide, pholcodine, proheptazoine, properidine, propiran, racemoramide, thebacon, trimeperidine and the pharmaceutically acceptable salts thereof. Still other addictive substances that can be utilized in the practice of the invention include the sedatives and hypnotics, e.g., benzodiazepines such as chlordiazepoxide, clorazepate, diazepam, flurazepam, halazepam, ketazolam, borazepam, oxazepam, prazepam, temazepam, triazolam and the pharmaceutically acceptable salts thereof, barbiturates such as amobarbital, ambobarbital, barbital, butabartital, mephobarbital, methohexital, pentobarbital, phenobarbital, secobarbital, talbutal, thiamylal and thiopental and the pharmaceutically acceptable salts thereof and other sedatives and hypnotics such as chloral hydrate, meprobamate, methaqualone, methyprylon and the pharmaceutically acceptable salts thereof. By way of inhibiting the development of tolerance to and/or dependence on any of the foregoing and similarly addictive substances, the addictive substance is administered before, with or following the administration of at least one nontoxic substance that blocks the N-methyl-D-aspartate (NMDA) receptor and/or at least one substance that inhibits the development of tolerance to and/or dependence on the addictive substance and is selected from the group consisting of morphinans, their mixtures or pharmaceutically acceptable salts thereof. Activation of the NMDA receptor, a subtype of excitatory amino acid receptors, induces a number of changes in the functional activity of nerve cells, and in particular, their capacity for excitability or inhibition in the presence of an addictive substance, via an increase in intracellular Ca++ concentration. The major consequences of NMDA receptor activation include the following sequences, or cascades, of events occurring within nerve cells: a) translocation and activation of protein kinases such as protein kinase C → phosphorylation of substrate proteins such as cytosolic enzymes, channel proteins, receptor proteins, etc. → changes in functional activity; b) initiation of early gene ( c-fos , c-jun , zif -268, etc.) expression by either increased intracellular Ca++ or Ca++-activated protein kinases → expression of functional genes responsible for production of cellular enzymes (such as protein kinases), receptor proteins (such as the NMDA receptor), ion channel proteins (such as K+, Na+, Ca++ channels), neuropeptides (such as dynorphin), etc. → changes in functional activity; c) Ca++/calmodulin (or other Ca++ binding proteins) induced activation of enzymes and other cellular components → activation of Ca++/calmodulin-protein kinase systems such as Ca++/calmodulin kinase II → autophosphorylation of enzymes (e.g., Ca++/calmodulin kinase II) or other functional proteins → changes in functional activity; d) Ca++/calmodulin induced activation of constitutive nitric oxide synthase as well as induction of inducible nitric oxide synthase → production of nitric oxide → i) production of cyclic guanosine monophosphate via activation of guanosine cyclase resulting in activation of protein kinases and early gene expression; ii) direct protein modification such as enzymes, receptor and/or channel proteins; iii) lipid membrane modification and/or nucleic acid modification via scavenge of free radicals; iv) induction of neurotoxicity at higher nitric oxide levels; v) retrograde actions in adjacent neurons or glial cells such as facilitation of glutamate release/NMDA receptor activation and/or inhibition of post-synaptic NMDA receptors → changes in functional activity; e) interactions with the cyclic adenosine monophosphate/protein /protein kinase A system, the phospholipase C-inositol triphosphate-Ca++/diacylglycerol-protein kinase system, the phospholipase A2-arachidonic acid/prostanoids/leukotrienes system → changes in functional activity induced by second messenger systems other than NMDA receptor/Ca ++ /Ca ++ -calmodulin/protein kinase systems; and, f) interactions with other excitatory amino acid receptor subtypes including non-NMDA receptors and metabotropic receptors as well as intracellular events subsequent to the activation of these excitatory amino acid receptor subtypes → changes in functional activity induced by the non-NMDA and metabotropic receptor activation. A substance that blocks the NMDA receptor will effectively prevent all of the foregoing major intracellular sequences of events from taking place. However, even with activation of the NMDA receptor, it is still possible to inhibit the development of tolerance to and/or dependence on an addictive substance by combining the addictive substance with a substance that blocks at least one of the foregoing major intracellular sequences of events. Thus, e.g., a substance that interferes with translocation and activation of protein kinase C or with calmodulin induced activation of constitutive nitric oxide synthase as well as induction of inducible nitric oxide synthase is also useful for the practice of this invention. Among the nontoxic substances that block the NMDA receptor and as such are useful in the practice of the present invention are morphinans such as dextromethorphan ((+)-3-hydroxy-N-methylmorphinan) and dextrorphan ((+)-3-hydroxy-N-methylmorphinan), their mixtures and the pharmaceutically acceptable salts thereof. Other useful nontoxic substances that block the NMDA receptor include ketamine (2-(2-chlorophenyl)-2-(methylamino)cyclohexanone), pyrroloquinoline quinone and cis-4-(phosphonomethyl)-2-piperidinecarboxylic acid. Administration of the composition of this invention can be in the form of a single dosage unit containing both the addictive substance and the nontoxic substance that blocks the NMDA receptor or the two substances can be administered separately provided both are ultimately present in effective amounts in the patient. Introduction of the composition into the patient can be by way of oral administration or by intravenous, intramuscular, subcutanous, intrathecal, epidural or intracerebroventrilcular injection. The preferred dosage of addictive substance and the nontoxic substance that blocks the NMDA receptor can vary widely, e.g., from about 0.25 to about 250 mg/day, but actual amounts will vary according to the particular active substances being used, the particular formulation containing the active substances and the state and circumstances of the host being treated. As those skilled in the art recognize, many factors that modify the action of the active substances herein will be taken into account by the treating physician such as the age, body weight, sex, diet and condition of the subject, the time of administration, the rate and route of administration, and so forth. Optimal dosages for a given set of conditions can be ascertained by those skilled in the art using conventional dosage determination tests in view of the experimental data provided herein. In alleviating withdrawal symptoms in addicted subjects deprived of the addictive substance, the substance that blocks the NMDA receptor can be administered to the subject, together with the addictive substance, at a dosage rate of about 0.25 to about 250 mg/day, again, specific dosage levels and routes of administration being selected in accordance with the subject's circumstances. As a result of this treatment, the subject will experience a reduced level of dependence on the addictive substance eventually reaching the point where total withdrawal of the substance will result in at most mild withdrawal symptoms. The composition herein can be formulated as a liquid, powder, elixir, injectable solution, etc. Formulations for oral use can be provided as hard gelatin capsules wherein the composition is mixed with an inert solid diluent such as calcium carbonate, calcium phosphate or kaolin, or as soft gelatin capsules wherein the composition is mixed with an oleaginous medium, e.g., liquid paraffin or olive oil. Aqueous suspensions can contain the composition in admixture with pharmaceutically acceptable excipients such as suspending agents, e.g., sodium carboxymethyl cellulose, methylcellulose, hydroxypropylmethylcellulose, sodium alginate, polyvinylpyrrolidone, gum tragacanth and gum acacia; dispersing or wetting agents such as naturally occurring phosphatide, e.g., lecithin, or condensation products of an alkylene oxide with fatty acids, e.g., polyoxyethylene stearate, or condensation products of ethylene oxide with long chain aliphatic alcohols, e.g, heptadecaethyleneoxycetanol, or condensation products of ethylene exide with partial esters derived from fatty acids and a hexitol, e.g., polyoxyethylene sorbitol monoleate or condensation products of ethylene oxide with partial esters derived from fatty acids and hexitol anhydrides, e.g., polyoxyethylene sorbitan monooleate. Such aqueous suspensions can also contain one or more preservatives, e.g., ethyl- or n-propyl-p-hydroxy benzoate, one or more coloring agents, one or more flavoring agents and one or more sweetening agents, such as sucrose, saccharin or sodium or calcium cyclamate. Dispersible powders and granules suitable for preparation of an aqueous suspension by the addition of water provide the composition in admixture with a dispersing or wetting agent, suspending agent and one or more preservatives. Suitable dispersing or wetting agents and suspending agents are exemplified by those already mentioned above. Additional excipients, e.g., sweetening, flavoring and coloring agents, can also be present. Syrups and elixirs can be formulated with sweetening agents, for example glycerol, sorbitol or sucrose. Such formulations can also contain a demulcent, a preservative and flavoring and coloring agents. The composition of this invention or either of its principal active ingredients can be provided in sustained release dosage form of which many kinds are known, e.g., as described in U.S. Patent Nos. 4,788,055; 4,816,264; 4,828,836; 4,834,965; 4,834,985; 4,996,047; 5,071,646; and, 5,133,974. The example which follows is illustrative of the invention. EXAMPLE 1 The effect of systemic dextrorphan on prevention of the development of morphine tolerance and dependence was examined in Sprague-Dawley rats weighing 350-400 gm. Morphine tolerance was developed in the rats by twice daily subcutaneous injection of 10 mg/kg morphine sulfate. The analgesic effect of the morphine was examined by using the well known tail-flick test which measures the latency of tail-flick upon radiant heat stimulation. The latency of tail-flick test is defined as the time elapsed from the onset of radiant heat to the flick of the rat's tail. In order to examine the effect of dextrorphan on the development of morphine tolerance, each morphine-treated rat also received intraperitoneal administration of either dextrorphan (1.56, 3.13, 6.25, 12.5 mg/kg, n=5/group) or saline (n=6) given 30 minutes prior to each morphine administration. Fig. 1 shows the effects of systemic doses of dextrorphan (DEX) on tolerance to morphine analgesia produced by twice daily subcutaneous administration of 10 mg/kg morphine. Each symbol represents mean tail-flick latency scores (those above 4.5 seconds reflect analgesia) for each group of rats (N=5-6) and vertical bars are standard errors in this and the other figures. Baseline scores were between 4 and 5 seconds (at Day 0) and post-drug scores measured 1 hour after drug administration were close to 10 seconds for the first 5 days of daily drug administration. The control group (open triangles) show marked reduction in response to morphine (i.e., tolerance) at 7 and 9 days. In contrast, dextrorphan potently prevented the development of morphine tolerance as shown by no significant decreases in tail flick latencies, i.e., remaining analgesic during the whole course of repeated morphine administration. Asterisks indicate mean scores that were significantly different from those of the control group. All tested doses of dextrorphan were effective in preventing development of morphine tolerance with optimal doses ranging from 3.13 mg/kg to 12.5 mg/kg. Fig. 2 shows the effects of systemic doses of dextrorphan on jumping, a withdrawal symptom produced by subcutaneous naloxone (2 mg/kg) in rats previously injected with morphine (10 mg/kg) twice daily for 9 days. Asterisks indicate median number of jumps in dextrorphan treatment groups (MOR + DEX) that were significantly less than that of the control group (MOR + SAL). Vertical bars refer to the range of the numbers of jumps. Thus, 3.13 and 6.25 mg/kg dextrorphan (but not 1.56 mg/kg) significantly reduced the incidence of jumping in morphine tolerant rats, a behavioral manifestation of morphine dependence, brought about following subcutaneous injection with 2 mg/kg naloxone. Thus, coadministration of dextrorphan with morphine greatly inhibits the development of both tolerance to and dependence on morphine while the analgesic effect of the morphine remains substantially unaffected.

Claims: A pharmaceutical composition comprising, in combination, an addictive substance selected from the group consisting of narcotic analgesics, sedatives, hypnotics, barbiturates and pharmaceutically acceptable salts thereof, and at least one non-toxic substance that blocks the N-methyl-D-aspartate receptor and/or at least one substance that inhibits the development of tolerance to and/or dependence on the addictive substance and selected from the group consisting of morphinans, their mixtures and their pharmaceutically-acceptable salts. The composition of Claim 1 wherein the addictive substance is selected from the group consisting of alfentanyl, alphaprodine, anileridine, bezitramide, codeine, dihydrocodeine, diphenoxylate, ethylmorphine, fentanyl, heroin, hydrocodone, hydromorphone, isomethadone, levomethorphan, levorphanol, metazocine, methadone, metopon, morphine, opium extracts, opium fluid extracts, powdered opium, granulated opium, raw opium, tincture of opium, oxycodone, oxymorphone, pethidine, phenazocine, piminodine, racemethorphan, racemorphan, thebaine, acetorphine, acetyldihydrocodeine, acetylmethadol, allylprodine, alphracetylmethadol, alphameprodine, alphamethadol, benzethidine, benzylmorphine, betacetylmethadol, betameprodine, betamethadol, betaprodine, clonitazene, cocaine, codeine methylbromide, codeine-N-oxide, cyprenorphine, desomorphine, dextromoramide, diampromide, diethylthiambutene, dihydromorphine, dimenoxadol, dimepheptanol, dimethylthiamubutene, dioxaphetyl butyrate, dipipanone, drotebanol, ethylmethylthiambutene, etonitazene, etorphine, ctoxeridine, furethidine, hydromorphinol, hydroxypethidine, ketobemidone, levomoramide, levophenacylmorphan, methyldesorphine, methyldihydro-morphine, morpheridine, morphine methylpromide, morphine methylsulfonate, morphine-N-oxide, myrophin, nicocodeine, nicomorphine, nicotine, noracymethadol, norlevorphanol, normethadone, normorphine, norpipanone, phenadoxone, phenampromide, phenomorphan, phenoperidine, piritramide, pholcodine, proheptazoine, properidine, propiran, racemoramide, thebacon, trimeperidine, chlordiazepoxide, clorazepate, diazepam, flurazepam, halazepam, ketazolam, borazepam, oxazepam, prazepam, temazepam, triazolam amobarbital, ambobarbital, barbital, butabartital, mephobarbital, methohexital, pentobarbital, phenobaibital, secobarbital, talbutal, thiamylal, thiopental chloralhydrate, meprobamate, methaqualone, methyprylon and pharmaceutically acceptable salts thereof. The composition of claims 1 or 2, wherein the morphinan is dextromethorphan, dextrorphan or mixtures or pharmaceutically acceptable salts thereof. A pharmaceutical composition according to claim 1 comprising, in combination, a narcotic analgesic and an NMDA receptor antagonist selected from dextromethorphan, dextrorphan, mixtures thereof and/or pharmaceutically acceptable salts thereof. The composition of Claim 4 wherein the narcotic analgesic is selected from the group consisting of alfentanyl, alphaprodine, anilerdine, bezitramide, codeine, dihydrocodeine, diphenoxylate, ethylmorphine, fentanyl, heroin, hydrocodone, hydromorphone, isomethadone, levomethorphan, levorphanol, metazocine, methadone, metopon, morphine, opium extracts, opium fluid extracts, powdered opium, granulated opium, raw opium, tincture of opium, oxycodone, oxymorphone, pethidine, phenazocine, piminodine, racemethorphan, racemorphan, thebaine and pharmaceutically acceptable salts thereof. The use of at least one non-toxic substance that blocks the N-methyl-D-aspartate receptor in the production of a composition effective in inhibiting the development of tolerance to and/or dependence on an addictive substance in mammals, and comprising the step of combining both said addictive substance and non-toxic substance prior to administration, wherein the non-toxic substance is selected from the group consisting of morphinans, their mixtures and their pharmaceutically acceptable salts, and wherein the addictive substance is selected from the group consisting of narcotic analgesics, sedatives, hypnotics, barbiturates and pharmaceutically acceptable salts thereof. The use according to Claim 5 wherein the addictive substance is selected from the group consisting of alfentanyl, alphaprodine, anileridine, bezitramide, codeine, dihydrocodeine, diphenoxylate, ethylmorphine, fentanyl, heroin, hydrocodone, hydromorphone, isomethadone, levomethorphan, levorphanol, metazocine, methadone, metopon, morphine, opium extracts, opium fluid extracts, powdered opium, granulated opium, raw opium, tincture of opium, oxycodone, oxymorphone, pethidine, phenazocine, piminodine, racemethorphan, racemorphan, thebaine, acetorphine, acetyldihydrocodeine, acetylmethadol, allylprodine, alphracetylmethadol, alphameprodine, alphamethadol, benzethidine, benzylmorphine, betacetylmethadol, betameprodine, betamethadol, betaprodine, clonitazene, cocaine, codeine methylbromide, codeine-N-oxide, cyprenorphine, desomorphine, dextromoramide, diampromide, diethylthiambutene, dihydromorphine, dimenoxadol, dimepheptanol, dimethylthiamubutene, dioxaphetyl butyrate, dipipanone, drotebanol, ethylmethylthiambutene, etonitazene, etorphine, etoxeridine, furethidine, hydromorphinol, hydroxypethidine, ketobemidone, levomoramide, levophenacylmorphan, methyldesorphine, methyldihydro-morphine, morpheridine, moiphise methylpromide, morphine methylsulfonate, morphine-N-oxide, myrophin, nicocodeine, nicomorphine, nicotine, noracymethadol, norlevorphanol, normethadone, normorphine, norpipanone, phenadoxone, phenampromide, phenomorphan, phenoperidine, piritramide, pholcodine, proheptazoine, properidine, propiran, racemoramide, thebacon, trimeperidine chlordiazepoxide, clorazepate, diazepam, flurazepam, halazepam, ketazolam, borazepam, oxazepam, prazepam, temazepam, triazolam amobarbital, ambobarbital, barbital, butabartital, mephobarbital, methohexital, pentobarbital, phenobarbital, secobarbital, talbutal, thiamylal, thiopental chloralhydrate, meprobamate, methaqualone, methyprylon and pharmaceutically acceptable salts thereof. The use according to claims 6 or 7 wherein the morphinan is dextromethorphan, dextrorphan or pharmaceutically acceptable salts thereof. The use according to claim 6 wherein the non -toxic substance that blocks the NMDA receptor is dextromethorphan, dextrorphan, mixtures thereof and/or pharmaceutically acceptable salts thereof and the addictive substance is a narcotic analgesic. The use according to Claim 9 wherein the narcotic analgesic is selected from the group consisting of alfentanyl, alphaprodine, anilerdine, bezitramide, codeine, dihydrocodeine, diphenoxylate, ethylmorphine, fentanyl, heroin, hydrocodone, hydromorphone, isomethadone, levomethorphan, levorphanol, metazocine, methadone, metopon, morphine, opium extracts, opium fluid extracts, powdered opium, granulated opium, raw opium, tincture of opium, oxycodone, oxymorphone, pethidine, phenazocine, piminodine, racemethorphan, racemorphan, thebaine and pharmaceutically acceptable salts thereof.

Inventors: LYLE JOHN W, MAO JIANREN, LYLE, JOHN W., MAO, JIANREN
Applicants: UNIV VIRGINIA COMMONWEALTH, VIRGINIA COMMONWEALTH UNIVERSITY
Application year: 1994
Main classification: A61K31
IPC codes: A61K31, A61P25, A61K45, A61P43